1. Field of the Invention
The invention relates to an inkjet cartridge for dispensing a predetermined amount of fluids; in particular, the invention relates to an inkjet cartridge with capillary tubes arranged in a high-density array.
2. Description of the Related Art
Advances in industries employing chemical and biological processes have created a need for devices that accurately and automatically dispense small quantities of liquids containing chemically or biologically active substances for commercial or experimental use. Accuracy and precision in the amount of liquid dispensed are important both from the standpoint of causing a desired reaction and minimizing the amount of material used. An example of a device with an array of reagents disposed thereupon is a biochip.
In FIG. 1a and FIG. 1b, a conventional apparatus for dispensing reagents disclosed in U.S. Pat. No. 6,001,309 is shown. FIG. 1a is an exploded top perspective view of the conventional dispensing apparatus. FIG. 1b is an enlarged, schematic, top perspective view of a setup of a nozzle delivery assembly of the conventional dispensing apparatus. Referring to FIG. 1a, the conventional dispensing apparatus 20 comprises a head assembly 21 having a plurality of nozzles (not shown). A base assembly 25 is provided with at least one reaction well 26 and a transport mechanism (not shown). An array of wells 26 is provided and formed in a microtiter plate 32. Referring to FIG. 1b, a delivery assembly 43 controls delivery of reagents 24 through nozzles to reservoirs 23. In the delivery assembly 43, the nozzles are coupled to reservoirs 23 by dispensing tubes 44.
However, such conventional dispensing apparatus is very complicated. Thus, its cost is expensive, and its assembly requires a large space.
Recently, inkjet printers have become established as reliable and efficient dispensing devices. However, there are two main concerns when applying the inkjet cartridges in the biological and chemical analysis. One is that the reagents the inkjet cartridge must be stored in a manner that provides a slight back pressure to the inkjet cartridge to prevent leakage from the inkjet cartridge when the inkjet cartridge is inactive. The other one is that the inkjet cartridge must avoid any intermixing of the different kinds of reagents.
FIG. 2 shows a conventional inkjet cartridge that can adjust its back pressure and is disclosed in U.S. Pat. No. 5,505,339. An accumulator 50 is configured to fit into an inkjet cartridge 52 including a reservoir 54 that hold a quantity of ink. The accumulator 50 includes an expandable bag 62 that is mounted to a spring 64. With such structure, the inkjet cartridge can adjust its back pressure based on environmental changes. Other conventional inkjet cartridges that can adjust its back pressure are disclosed, in U.S. Pat. No. 5,526,030, U.S. Pat. No. 4,771,295, U.S. Pat. No. 5,047,790, U.S. Pat. No. 5,409,134, and U.S. Pat. No. 5,998,803.
However, conventional inkjet cartridges that can adjust their back pressure are very complicated in structure. In addition, after dispensing, the mount of the ink remaining in the inkjet cartridge is so large that it is difficult to deal with.
FIG. 3a and FIG. 3b shows a conventional inkjet cartridge that can avoid intermixing of the different kinds of inks, which is disclosed in U.S. Pat. No. 5,497,178. FIG. 3a is a perspective, sectional view of a print head body of the conventional inkjet cartridge as disclosed in U.S. Pat. No. 5,497,178, and FIG. 3b is a bottom view of the printer head body in FIG. 3a. A conventional inkjet cartridge 60 includes a print head body 61 containing three standpipe portions 62, 63, and 64. The standpipes 62, 63 and 64 are located in separate ink chambers 66, 67, 68, respectively. Exit ports 71, 72 and 73, as shown in FIG. 3b, communicate with the ink chambers 66, 67, 68, respectively. An opening 77 in the bottom of the standpipe 62 allows ink to flow downwardly into a crossflow channel 81. An opening 78 in the bottom of the standpipe 64 allows ink to flow downwardly into a crossflow channel 82. The crossflow channel 81 slopes downwardly and forwardly, terminating in a reduced cross-section portion 83 which in turn leads to the exit port 71. Similarly, the crossflow channel 82 slopes downwardly and forwardly, terminating in a reduced cross-section portion 84 which in turn leads to the exit port 73. With such structure, the inkjet cartridge can avoid intermixing of the different kinds of inks. Other conventional inkjet cartridges that can avoid intermixing of the different kinds of inks are disclosed, for example, in U.S. Pat. No. 5,659,345 and U.S. Pat. 5,831,653.
However, all of the conventional inkjet cartridges that can avoid intermixing of the different kinds of inks are very complicated in structure. In addition, it is difficult to apply conventional inkjet cartridges used in a dispensing device in which the amount of the dispensing fluid is very small.